m (→TalkTalk lines: typo)
The downside is that, whilst the overall speed is the same, interleaving adds latency. Typically around 8ms is added to all communications on the line, though there are different levels of interleaving (or Impulse Noise Protection) which cause even higher latency. The latency added is however consistent, which can, in itself, be an important factor for on-line games.
This is a slight challenge: with interleaving the line has extra latency all the time, but without it you get errors. When there is an error then the packet has to be resent, which adds a lot more latency but randomly and inconsistently. Usually interleaving is a better choice, but it does depend
There is often one other option, which is running the line at a lower speed. This can remove the interference if it is only at certain frequencies, and as we explained above, the speed is not necessarily a key factor.